Conventional passive, semi-active, and active hydraulic dampers and shock absorbers typically include a piston and an attached piston rod that move through a cylindrical housing in response to forces applied by the vehicle body, the road surface, and/or a source of hydraulic pressure. Occasionally, operating conditions are such that the piston travel relative to the housing may be excessive, i.e. beyond its normal stroke. Under such circumstances, the piston, or other elements that move relative to the housing, may collide with objects located at either end of the housing that remain stationary relative to the housing. Bump stops, typically fabricated from relatively soft materials, such as for example, rubber or plastic, may be used at one or both ends to diminish the damage that may result from such collisions. However, bump stops made of rubber and other similar materials do not always offer sufficient protection, can be noisy, and can be easily damaged so that they no longer function properly. High forces and temperatures may also cause such bump stops to be extruded and/or migrate from their original configurations, or otherwise interfere with the operation or performance of other components in the housing, such as for example, diverter valves. Repeated impact may also cause pieces of the bump stop to break off and be carried to other parts of the system, for example, in a hydraulic active suspension fluid circuit, which may result in a partial or complete system failure.
When a piston moves through a shock absorber or actuator housing, it typically displaces a quantity of fluid at a rate that is proportional to the speed of the piston. In vehicle active suspension systems, at least one diverter valve may be used to at least partially divert hydraulic fluid displaced by the movement of the piston away from a hydraulic pump that normally would receive this fluid. Such a diverter valve is typically a passive valve that is activated in response to the hydraulic fluid flowing at a rate that exceeds a fluid diversion threshold.